I don't think it's being pedantic. I think it's just interpreting the data correctly.Ok, I think this is pedantics a little - the definition of overperformance is "To perform better than expected" which in Coburn's case he is performing better than his xG would suggest.
I don't think this is a bad thing. I agree he is finishing his chances well.
And I think this is what I would confirm from watching them both as well - Coburn has scored some good goals this season whilst Lath has been a bit wasteful (but this has improved - he was underperforming v xG earlier in the season)
Archer outscored his xG comfortably last season because he's a good finisher. Your some how spinning the fact that Coburn has scored more goals than expected into a negative. When it should be seen as a positive.